Originally published 2021-09-26.
In late September 2021, a short phone video from the Bronx Zoo in New York spread quickly online. It showed two western lowland gorillas in the zoo's Congo Gorilla Forest engaging in oral sex while visitors, including young children, watched through the glass. Some adults steered their kids away; others kept filming. The clip prompted embarrassed laughter, a few complaints and plenty of questions about whether gorillas really behave this way.
The short answer is yes. Sexual behaviour that has nothing to do with making babies has been recorded in gorillas both in zoos and in the wild, and in many other primates. What happened in the Bronx was unusual to witness, but it was not unnatural for the animals involved.
What visitors saw at the Congo Gorilla Forest
The video was taken inside the Congo Gorilla Forest, a 6.5-acre indoor and outdoor rainforest habitat that opened at the Bronx Zoo in 1999. The exhibit is run by the Wildlife Conservation Society, which manages the zoo, and it houses two troops of western lowland gorillas alongside hundreds of other animals from Central African forests.
In the footage, the pair carry on in plain view, apparently unbothered by the crowd. Gasps and nervous exclamations can be heard in the background as people realise what they are looking at.
The father who recorded it had come with his four-year-old daughter and his niece, and told the New York Post that he had been filming plenty because his wife was waiting outside with their sleeping son. His reaction summed up the mood of the room: I was shocked and had no idea that was a 'natural' act.
The zoo did not publicly comment on the clip at the time. Press reports added that similar behaviour had reportedly been seen in the same habitat the year before, although that earlier episode was not filmed and cannot be confirmed.
Is this normal gorilla behaviour?
Researchers who study great apes have documented a wide range of sexual behaviour that does not lead to conception. In western lowland gorillas, females living in one-male groups have been observed engaging in sexual activity at every stage of their reproductive cycle, including while pregnant or nursing. Some scientists link this to competition between females: staying sexually active with the group's silverback may reduce the chances that rivals conceive.
Same-sex behaviour has also been recorded. The best-known study came from Rwanda, where Cyril Grueter of the University of Western Australia and colleagues analysed observations of wild mountain gorillas in the Virunga volcanoes, with support from the Dian Fossey Gorilla Fund. Of 22 adult females they followed, 18 took part in sexual contact with other females. The work was published in the journal PLOS ONE in 2016.
The team tested three ideas: that the behaviour expressed dominance, strengthened friendships or helped patch things up after fights. None held up consistently. Instead, the researchers leaned toward a simpler explanation. Same-sex contact was more common at times when the females were also mating with males, and females whose advances had been ignored by a male seemed to redirect that interest. Grueter put it plainly to reporters: My impression is that these females derive pleasure from sexual interaction with other females.
Why it looks shocking to us
Much of the uproar came from people projecting human rules onto animals. Gorillas do not share our ideas of privacy, modesty or what is suitable for children. They live in close-knit family groups, usually led by one adult male, and everyday life, from eating and grooming to squabbling and mating, happens in front of the whole troop.
A zoo enclosure simply places that ordinary life in front of a new audience. Words like "shameless" or "scandal" say a lot about the onlookers and very little about the gorillas. The animals were not performing, protesting or misbehaving; they were doing something that their species does.
It also helps to remember how closely related we are. Gorillas share most of their DNA with humans, and like chimpanzees and bonobos they use touch and sexual contact in social ways. Bonobos in particular are famous among biologists for using sex to ease tension within a group. Seen in that context, a moment that felt outrageous in a crowded viewing gallery looks much more like ordinary primate biology.
What zoos can and cannot do
Could the Bronx Zoo have prevented the scene? Realistically, no. Modern zoos aim to let animals behave as naturally as possible, and suppressing normal social or sexual behaviour would run against good welfare practice. Keepers can manage group make-up and breeding through veterinary means, but they do not schedule when animals interact.
What zoos can do is help visitors understand what they are seeing. Keepers and educators are often present at popular exhibits and answer questions. Signs and talks about gorilla family life, mating and parenting give context that a ten-second viral clip never will.
There is also a conservation angle. Western lowland gorillas are listed as Critically Endangered by the IUCN, threatened by hunting for bushmeat, habitat loss and disease, including outbreaks of Ebola that have killed large numbers of wild apes. Zoo-based breeding programmes manage the captive population carefully, so healthy reproductive and social behaviour in groups like the Bronx troops is something keepers want to see.
Talking to children about it
If you visit a zoo and something like this happens in front of your children, there is no need for panic. A calm, simple explanation usually works best, pitched to their age. Many parents find phrases like these helpful:
- For young children: "The gorillas are showing they like each other. Animals don't wear clothes or close doors like people do."
- For older children: "Animals mate to have babies, and sometimes just to bond with each other. It's a normal part of nature."
- For curious teenagers: it can be a chance to talk about animal behaviour, evolution and the science behind what they saw.
Moving along to the next exhibit is also perfectly fine. Children tend to take their cue from adults; if you treat it as an ordinary part of animal life, most will quickly lose interest.
Common myths about animal sexuality
- "Animals only have sex to reproduce." Not true for many species. Non-reproductive sex is well documented in great apes, dolphins and other social mammals.
- "Same-sex behaviour only happens in captivity." The Rwandan study involved wild mountain gorillas, and similar behaviour is recorded in many free-living species.
- "Zoo animals behave this way because they are bored." Boredom can affect captive animals, but the behaviour itself is part of the natural repertoire seen in the wild.
The Bronx Zoo clip was a brief, awkward moment for a few families. For anyone curious, it is also a reminder that our closest relatives have rich social lives, and that the best response to surprising animal behaviour is usually to learn a little more about it.
Sources: New York Post (September 2021, original report and quote); LADbible; Phys.org on Grueter et al., PLOS ONE 2016; Bronx Zoo (Wikipedia); Western lowland gorilla (Wikipedia). Video: YouTube upload of the visitor's footage.
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